The iAudio 9 is a nice player as it is, but it could certainly do with a few improvements (same as every other gadget ever made). Most of the points below aren't really i9-specific, but would be nice on any other Cowon player as well, like the S9 or D2+. Feel free to add to this thread with constructive suggestions.

Resume: Same as the D2 and S9, the i9 does not resume playback, it only remembers its place in a file but always starts on the main screen. Meaning, one always has to go to the audio or video screen and has to press play. This is tedious and should be fixed - resume means resume, not remember. Users fixed that flaw on the D2 and S9 on their own, with custom UCIs. This should really be fixed in the firmware (not only for the i9, but also the S9 and D2/D2+).

Center button: Give us the option to disable the A-B repeat function on the center button, or let us remap the button to something else. File info display comes to mind, same as on the S9. Touching the AB-repeat by mistake can happen quite easily, and it's really annoying when it happens. I'm not saying to get rid of AB-repeat entirely, there are people who want that function - just make it optional.

Wallpaper support on the primary main menu screen: I have no idea why Cowon only implemented wallpaper support on the secondary, much less useful main screen, but it is extremely simple to fix. I already fixed it. Please just implement it in the firmware.

Recent files list: There's a lot wrong with the Cowon O2, but one of its features is pure genius: the recent files list. It's like a bookmark list, but without one having to actually set any bookmarks. It just remembers all audio and video files one didn't finish to listen/watch, and one just selects a file from the list to continue. A simple and perfect solution. Please implement it on your other players as well.

AAC support: AAC is perhaps the second most widespread audio codec nowadays, after MP3. It's technically on par with Vorbis, and it's a lot more advanced and better than WMA. It really needs to be supported on all Cowon players, not just underdogs like the O2. Not sure what the licensing status is for AAC, but in any case it's way more useful than supporting APE and similar obsolete formats.

Replaygain support: One of the most awesome features for me, currently supported by Rockbox, Sandisk players, and every decent software audio player, like Winamp or Foobar. I wish Cowon would support Replaygain, it would be the next logical step after gapless to make them true 'audio aficionado' gear. Replaygain information.

Line-out for audio: The video-out cable seems to deliver line-level audio (more or less). It's a shame there's no real line-out for regular audio/music tracks on any Cowon player. It would be beneficial for hooking up the player to a stereo, portable headphone amplifier, and such - contrary to using the pre-amplified headphone output. iPods, some Sansas, and a few other players have dedicated line-out. Since Cowon players are regarded as being high quality audio players, it would only be logical if they would cater to the headphone amps crowd as well.

Last.fm scrobbling in MSC mode: One can only dream... but Rockbox can scrobble in MSC mode by simply writing a text file to the player's memory. I would love to have that feature on a Cowon. Scrobbler information.